1. Field of the Invention
The present invention relates to a touch panel for inputting coordinates on a screen and a display device using the same. In particular, the present invention relates to a technology for enabling an input of a touch panel of capacitive coupling type using such an insulator as a resin pen.
2. Description of the Related Art
A display device including an input device (hereinafter, also referred to as “touch sensor” or “touch panel”) having an on-screen input function of inputting information to a display screen by a touch operation (contact and press operation, hereinafter, simply referred to as “touch”) with a user's finger or the like is used for mobile electronic devices such as a PDA and a mobile terminal, various home electric appliances, a stationary customer guiding terminal such as an automatic reception machine, and the like. As the input device using the touch, there are known resistance film type of detecting a change in resistance value of a touched portion, capacitive coupling type of detecting a change in capacitance thereof, optical sensor type of detecting a change in amount of light at the portion shielded by the touch, and the like.
The capacitive coupling type has the following advantages when compared with the resistance film type or the optical sensor type. For example, a transmittance of the resistance film type or the optical sensor type is as low as 80%. On the other hand, a transmittance of the capacitive coupling type is as high as about 90%, thereby preventing a reduction in displayed image quality. In the resistance film type, a touch position is detected by mechanical contact to the resistance film, thereby leading to possible deterioration or breakage (crack) of the resistance film. On the other hand, in the capacitive coupling type, there is no mechanical contact such as contact of a detection electrode with another electrode. Thus, the capacitive coupling type is advantageous in durability.
An exemplary capacitive coupling type touch panel is disclosed in U.S. Pat. No. 7,030,860. In the capacitive coupling type touch panel disclosed therein, a vertical detection electrode (X electrode) and a horizontal detection electrode (Y electrode) are arranged in vertical and horizontal two-dimensional matrix, and a capacitance of each electrode is detected by an input processing part. When a conductor such as a finger touches a surface of the touch panel, the capacitance of each electrode increases. Thus, the input processing part detects the increase to calculate input coordinates based on a signal of a capacitance change detected by each electrode. Even when the detection electrode is deteriorated to change its resistance value as physical characteristics, such an influence on capacitance detection is limited. Thus, there is only a little influence on input position detection accuracy of the touch panel. As a result, high input position detection accuracy may be realized.